Conventional drill bits are used on a daily basis for performing almost a limitless number of drilling operations. An example of one particular operation is the drilling of railway track sections to receive bolts for securing the sections to one another in an end to end manner. The drill bit is secured in an appropriate drill with the cutting end exposed for the drilling operation. However, after numerous uses, the cutting end becomes quite dull and either has to be resharpened or discarded, thereby necessitating the use of a new drill bit. The sharpening and/or replacement of the drill bit is both time consuming and costly.
Suggestions have been made in the past to provide drill bits which are double ended, i.e. drill bits which have a cutting edge at both ends. The provision of a double ended cutting bit would appear to be extremely beneficial in that they are only slightly more costly than the single ended drill bit and they require sharpening or replacement only half as often as a conventional drill bit.
Even in view of the fact that the double ended drill bit has extremely desirable characteristics, it has met with very limited success because a double ended drill bit can not be properly secured in a drill chuck. The secured cutting end rides on the chuck pin which not only cuts into and damages the pin but also dulls the cutting edges of the bit, thereby rendering them ineffective when the bit is reversed. Therefore, according to conventional practice, the provision of the second cutting end on the bit is more of a hindrance than a help. The problem is augmented by the fact that all the drilling pressures further tend to drive the bit into the chuck pin.
The present invention provides an answer to these problems in the form of a cutting end protector for use in securing a double ended drill bit in a drill chuck. As a result, the economic and other benefits of a double ended drill bit can be reaped without any concern for the drill.
The cutting end protector of the present invention comprises a body portion adapted to fit in the drill chuck and located therein by a chuck pin. The body portion has a cutting end receiving face provided with a central recess for receiving the point of a bit cutting end and a pair of chamfered or bevelled face portions diverging outwardly and forwardly, of the body portion one on either side of the central recess. The chamfered face portions are slanted in opposing directions for fitting with the cutting edge trailing surfaces, so that the cutting edges are neither dulled or come into contact with the drill chuck pin.